<!doctype html>
<html>
<body>
    <script type="text/javascript">
        var request = new XMLHttpRequest();
        request.open('GET', 'additionalresponseheadershandler:about', /* async = */ false);
        request.send();
        var headers = request.getAllResponseHeaders();
        console.log("TST_ADDITIONALRESPONSEHEADERS;" + headers);
    </script>
</body>
</html>
